[PATCH v2 11/12] ARM: wire up UEFI init and runtime support

[Ard Biesheuvel]

On 16 November 2015 at 20:01, Russell King - ARM Linux
<linux at arm.linux.org.uk> wrote:
> On Mon, Nov 16, 2015 at 07:32:36PM +0100, Ard Biesheuvel wrote:
>> +static inline void efi_set_pgd(struct mm_struct *mm)
>> +{
>> +     if (unlikely(mm->context.vmalloc_seq != init_mm.context.vmalloc_seq))
>> +             __check_vmalloc_seq(mm);
>> +
>> +     cpu_switch_mm(mm->pgd, mm);
>> +
>> +     flush_tlb_all();
>> +     if (icache_is_vivt_asid_tagged())
>> +             __flush_icache_all();
>> +}
>
> I don't think that's sufficient.  There's a gap between switching the mm
> and flushing the TLBs where we could have different global TLB entries
> from those in the page tables - and that can cause problems with CPUs
> which speculatively prefetch.  Some CPUs raise exceptions for this...
>

OK. So you mean set TTBR to the zero page, perform the TLB flush and
only then switch to the new page tables?